MINI SPT FOR RURAL GEOTECHNICAL INVESTIGATIONS

Abstract

The Standard Penetration Test is an indispensable part of any geotechnical investigation, carried out for design-ing a foundation in coarse grained deposits. However this test is unsuitable for rural geotechnical investigation because of its heavy weight and high relative cost. Therefore based on the principles of SPT, and keeping the requirements of rural geotechnology in mind , a Mini SPT has been designed and fabricated. The main differences between a ctual SPT and the Mini SPT apparatus are (a) The energy is supplied by a smaller hammer weighing 6.5 kg and falling through 37.5 cm. (b) The size of the sampler is smaller with an outer diameter of 26 mm and having an area ratio of 53/. (c) The penetration value is taken as the number of blows required forla.st 10 cm of penetration, after an initial seating drive of 5 cm. Thus the complete equipment is lighter weighing just about 60 kg, and two persons cane asily transport and conduct the tests at the site. Based on data collected from an extensive field testing programme, carried Dut all over Roorkee, the following correlation between Mini SPT and actual SPT penetration values is suggested: Penetration value of Penetration value of Mini SPT actual SPT Vi Thus knowing the penetration value of actual SPT from the above relationship, the soil properties can be found by using standard correlations, and the foundation can be designed.